The central features of the future fourth-generation
mobile communication systems are the provisioning of highspeed
data transmissions (up to 1 Gb/s) and interactive
multimedia services. For effective delivery of these services,
the network must satisfy some stringent quality-of-service
(QoS) metrics, defined typically in terms of maximum delay
and/or minimum throughput performances. Mobile satellite
systems will be fully integrated with the future terrestrial
cellular systems, playing important roles as back-bones or
access satellites, to provide ubiquitous global coverage to
diverse users. The challenges for future broadband satellite
systems, therefore, lie in the proper deployments of state-ofthe-
art satellite technologies to ensure seamless integration of
the satellite networks into the cellular systems and its QoS
frameworks, while achieving, to the extent possible, efficient
use of the precious satellite link resources. This paper presents
an overview of the future high-speed satellite mobile
communication systems, the technologies deployed or planned
for deployments, and the challenges.